Core-sheath compounded yarn and a woven/knitted fabric having excellent covering property and abrasion resistance

ABSTRACT

The present invention provides a core-sheath compounded yarn constituted from a high tenacity and high heat-resistant fiber and other dyeable fiber and/or dope-dyed yarn where the high tenacity and high heat-resistant fiber is arranged as a core yarn while other dyeable fiber and/or dope-dyed yarn are/is arranged in a substantially untwisted state and the surroundings thereof are spirally covered by dyeable fiber and/or dope-dyed yarn. A woven/knitted fabric where the core-sheath compounded yarn is at least partially used is also provided.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a core-sheath compounded yarn having excellent covering property, abrasion resistance, heat resistance and cut resistance and, more particularly, it provides a core-sheath compounded yarn comprising polybenzazole fiber and p-aramid fiber having sensuousness and light resistance by compounding them with dyeable fiber and/or dope-dyed yarn making the best use of high tenacity and heat resistance of polybenzazole fiber and p-aramid fiber. A woven/knitted fabric comprising this core-sheath compounded yarn is particularly useful in, for example, uniform, fireproof clothes, work clothes, special protective clothes, outdoor clothing, racing wear or sport clothing used under severe conditions as well as suits, jeans, bag material, roof fabric, gloves, socks, sawing thread, etc.

BACKGROUND ART

As a high tenacity fiber material used for fabric having a protective function, wholly aromatic polyester, ultrahigh molecular weight polyethylene fiber, etc. have been known already while, as a fiber material having a heat resistant characteristic, aromatic m-aramid fiber, polyamide imide fiber, polyimide fiber, polyphenylene sulfite fiber (PPS), flame resistant fiber and fluorine fiber have been known and, further, as a fiber material having high tenacity and heat resistance, p-aramid fiber has been known. An intensified fabric making the best use of those characteristics has been used in uniform, fireproof clothes, work clothes, outdoor clothing, racing wear or sport clothing used under severe conditions as well as suits, jeans, bag material, gloves, etc. On the other hand, as other high tenacity and heat-resistant fiber exceeding these fibers, a polybenzazole fiber constituted from polybenzoxazole, polybenzothiazole or copolymer thereof has been known and an intensified fabric using said fiber has been expected. Please see The Seni Kagaku, August/September, p. 32-36 (1998) and Textile Processing Technology, Vol. 34, No. 9, p. 12-15 (1999).

However, although p-aramid fiber and polybenzazole fiber have an excellent heat resistance and dynamic property, they have, on the other hand, inconveniences that they are apt to be discolored by light such as sunlight, incandescent lamp or fluorescent lamp and their tenacity lowers by exposing thereto for long time resulting in lowering of tear strength and abrasion strength. In order to improve such inconveniences, investigations such as addition of a light resistant agent have been conducted (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2001-11311) but there have been an economical problem that productivity lowers when an additive is made to contain therein and inherently expensive fiber becomes more expensive and a problem that the additive badly affects in the after-treatment or during the use.

DISCLOSURE OF THE INVENTION Problem That the Invention is to Solve

The present invention has been achieved on the background of the problems in the prior art and is to provide, at a low cost, a compounded yarn being excellent in light resistance and heat resistance, maintaining tear resistance, abrasion resistance and cut resistance for a long period, and being suitable for use in uniform, fireproof clothes, work clothes, special protective clothes, outdoor clothing, racing wear or sport clothing used under severe conditions as well as suits, jeans, bag material, roof fabric, gloves, socks, sawing thread, etc.

Means for Solving the Problem

The present inventors have intensively carried out the studies for solving the above problems and achieved the present invention. Thus, the present invention is: (1) a core-sheath compounded yarn constituted from a high tenacity and high heat-resistant fiber and other dyeable fiber and/or dope-dyed yarn where the high tenacity and high heat-resistant fiber is arranged as a core yarn while other dyeable fiber and/or dope-dyed yarn are/is arranged in a substantially untwisted state and the surroundings thereof are spirally covered by dyeable fiber and/or dope-dyed yarn; (2) the core-sheath compounded yarn according to (1) where said high tenacity and high heat-resistant fiber is polybenzazole fiber and/or p-aramid fiber; (3) the core-sheath compounded yarn according to (1) where said dyeable fiber and/or the dope-dyed yarn are/is m-aramid fiber and/or polyamide imide fiber; and (4) a woven/knitted fabric where the core-sheath compounded yarn according to (1) is at least partially used.

ADVANTAGES OF THE INVENTION

In accordance with the present invention, there are advantages as compared with the conventional core-sheath compounded yarn that a compounded yarn having a significantly improved covering property is achieved and that a heat resistant compounded yarn having improved light resistance, having fully drawn-out properties of high tenacity and high heat-resistance fiber, being excellent in tear resistance, abrasion resistance, cut resistance and heat resistance, also having sensuousness, and being suitable for use in uniform, work clothes, outdoor clothing, racing wear or sport clothing used under severe conditions as well as suits, jeans, bag material, roof fabric, gloves, socks, sawing thread, etc. is able to be provided at a low cost.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be illustrated in detail as follows.

The compounded yarn of the present invention is preferably a core-sheath compounded yarn constituted from a high tenacity and high heat-resistant fiber (fiber A) and other dyeable fiber and/or dope-dyed yarn (fiber B) where the high tenacity and high heat-resistant fiber (fiber A) is arranged as a core yarn while other dyeable fiber and/or dope-dyed yarn (fiber B) are/is arranged in a substantially untwisted state and the surroundings thereof are spirally covered by dyeable fiber and/or dope-dyed yarn (fiber C).

The reason therefor is that, as a result of preparing a core-sheath compounded yarn having such a constitution, excellent properties of high tenacity and high heat-resistance fiber are fully able to be drawn out.

Thus, although a high tenacity and high heat-resistant fiber has excellent dynamic and heat resistant properties, it has a problem on the other hand that light resistance is poor and, when exposed to light, physical properties significantly lower. Therefore, when it is used outside for long time, there maybe a means that light is shielded by a coating or a film in dark color but there are problems such as that texture becomes bad or convenience is deteriorated in using as a clothing if coating, film, etc. are used. Further, it is also considered to compound with other material as in the case of the known compounded yarns (for example, see Japanese Patent Application Laid-Open (JP-A) No. 189074/95 and Japanese Patent Application Laid-Open (JP-A) No. 54229/95) but, in the compounded yarn as such, a high tenacity and high heat-resistant fiber is -exposed on the surface of the compounded yarn whereby no sufficient effect is able to be achieved. In the case of the present invention, fiber A is covered by fiber B in a substantially untwisted state whereby the fiber A is hardly exposed on the surface of the compounded yarn and, further, an excellent covered state is fixed by a fiber C whereby delivery of light to the fiber A is effectively prevented resulting in an excellent light shielding property.

The high tenacity and high heat-resistant fiber (fiber A) of the present invention is a fiber where tenacity is not less than 15 cN/dtex and Loi value is not less than 25 and its examples include polybenzazole fiber and p-aramid fiber. Among them, polybenzazole fiber is particularly preferred in view of its excellent heat resistance and, if economical view is also taken into consideration, p-aramid fiber is preferred as well. Although there is no particular problem for the upper limits of the tenacity and the Loi value, it is technically difficult and practically less-useful that the tenacity exceeds 70 cN/dtex and the Loi value exceeds 100.

The polybenzazole fiber used in the present invention is a fiber comprising a polybenzazole polymer and the polybenzazole (PBZ) is a polybenzoxazole (PBO) homopolymer, a polybenzothiazole (PBT) homopolymer or a random, sequential or block copolymer of the PBO and PBT. Tensile strength of those fibers is not less than 30 cN/dtex or, preferably, not less than 33 cN/dtex.

There is no particular limitation for the form of the high tenacity and high heat-resistant fiber (fiber A) used in the present invention but any of monofilament, multifilament, twisted yarn, spun yarn, stretch broken spun yarn, air-jet textured yarn and crimp textured yarn may be used.

A dyeable fiber used for the fiber B or the fiber C of the present invention means a fiber which is used for common clothes and for industry being able to be dyed with direct dye, vat dye, naphthol dye, sulfur dye, disperse dye, reactive dye, acidic dye, cationic dye, etc. and examples thereof include natural fiber such as cotton, wool, animal hair or hemp and synthetic fiber such as polyester, nylon, rayon, acetate, acrylate, Vinylon, wholly aromatic aramid fiber, polyamide imide fiber or polyimide fiber. Although there is no particular limitation therefor, m-aramid fiber and polyamide imide fiber which do not cause melting and thermal fusion upon abrasion are particularly preferred.

Among those dyeable fibers, natural fiber such as cotton, wool, animal hair or hemp and synthetic fiber such as polyester, nylon, rayon, acetate, acrylate or Vinylon are preferred to be endowed with flame resistance when their use as heat resistant and flame resistant fabric is taken into consideration. For example, the cellulose type fiber endowed with flame resistance is the so-called flame retardant cellulose type fiber having a flame resistance and, to be more specific, it is cotton, rayon or polynosic fiber where 1 to 5% by weight of phosphorus atom is added to the fiber weight or a mixture with such a fiber or, more preferably, in addition thereto, it is the above fiber where 0.5 to 3% by weight of nitrogen atom is added to the fiber weight. It is also the above cellulose type fiber where a limit oxygen index (LOI value) evaluated according to JIS K 7201 is not less than 23, preferably not less than 25 or, more preferably, not less than 27. When the amount of phosphorus is 1% or less, the endowed resistance to flame is not sufficient while, when it is more than 5%, it badly affects the manufacturing steps or badly affects the tenacity as the fiber. As to the cotton endowed with flame resistance for example, cotton which is subjected to an after-treatment with the contained phosphorus and/or the contained nitrogen compound(s) is preferred. Although a polynosic fiber or a rayon endowed with flame resistance may also be that which has been subjected to an after-treatment, it may also be a fiber where a polyphosphonate compound of about 500 to 10,000 molecular weight is added to an original spinning solution for the manufacture of a viscose artificial fiber as mentioned, for example, in Japanese Examined Patent Application (JP-B) No. 2693/73 followed by spinning by a conventional method. Examples of the wool to which flame resistance is endowed include those where a specific zirconium or titanium compound is chemically bonded.

Examples of the dope-dyed yarn used for the fiber B and the fiber C of the invention of the present application include a synthetic fiber such as polyester, nylon, polyethylene, polypropylene, rayon, acetate, acrylate, Vinylon, wholly aromatic aramid fiber, polyamide fiber, polyamide imide fiber, polyimide fiber, polyphenylene sulfite fiber (PPS), flame resistant fiber, fluorine fiber, polybenzimidazole fiber or polyallylate fiber and, although there is no particular limitation therefor, m-aramid fiber and polyamide imide fiber which do not cause melting or thermal fusion upon abrasion are preferred.

As to the fiber B or the fiber C used for the compounded yarn of the present invention, it is preferred to be m-aramid fiber, polyamide imide fiber, polyimide fiber, PPS fiber or a fluorine fiber so as to supplement the heat resistance and tenacity inherent to the high tenacity and high heat-resistant fiber A. In view of a light shielding property, the fiber where m-aramid fiber, polyamide imide fiber, polyimide fiber, PPS fiber or fluorine fiber is dyed or dope-dyed is more preferred and the fiber which is dyed into dark color such as black or dark blue color is particularly preferred.

The compounded yarn of the present invention also has the advantages that, with regard to the thermal shrinkage which is particularly grasped as a disadvantage in m-aramid fiber, PPS fiber, etc., shrinkage of the fiber B is suppressed by a support of the fiber A when the fiber as such is used as the fiber B while, when it is used as a fiber C, it strongly restrains the fiber A and the fiber B due to thermal shrinkage whereby an excellent covering property is strongly fixed.

There is no particular limitation for the form of the fibers A, B and C used in the present invention but any of monofilament, multifilament, twisted yarn, spun yarn, stretch broken spun yarn, air-jet textured yarn and crimp textured yarn may be used and, among them, the case where the fiber A is filament and the fiber B is staple or crimp textured yarn is particularly preferred. The reason is that, when the fiber A is made into filament, high tenacity is able to be kept while, when the fiber B is made into staple or crimp textured yarn, the volume is able to be made high whereby the gap in the fiber B through which light comes in is reduced and a light shielding property is able to be enhanced.

The core-sheath compounded yarn in the present invention is a core-sheath compounded yarn constituted from a high tenacity and high heat-resistant fiber and other dyeable fiber and/or dope-dyed yarn where the high tenacity and high heat-resistant fiber is arranged as a core yarn while other dyeable fiber and/or dope-dyed yarn are/is arranged in a substantially untwisted state and the surroundings thereof are spirally covered by dyeable fiber and/or dope-dyed yarn. With regard to a woven/knitted fabric using this compounded yarn, there is no particular limitation for its tissue and structure but a double weave having front and back surfaces may be acceptable as well. It is also possible to use this compounded yarn partially and this compounded yarn may be also used, in combination with other material, as twisted union yarn, union cloth, or union knit, or it may be used as grid yarn, i.e. so-called rip stop. It is further possible that the compounded yarn of the present invention is used for making into braid, plaiting, twisted yarn, rope or cable.

In the compounded yarn of the present invention, the ratio by weight of the fiber A forming the core to the sheath (fiber B) is preferred to be from 5 to 50% by weight. When it is less than 5% by weight, there is no contribution of the high tenacity and high heat-resistant effect of the fiber A while, when it is more than 50% by weight, the core is exposed whereby no beautiful appearance is available and resistance to light lowers. The ratio by weight of the fiber A is preferably from 5 to 45% by weight or, more preferably, from 10 to 40% by weight.

EXAMPLES

The present invention will now be illustrated by way of the following Examples although the present invention is not limited thereto unless it surpasses the gist of the invention.

Example 1

A spinning dope where cis-polybenzoxazole having a limiting viscosity of 30 dl/g was dissolved in polyphosphoric acid in a concentration of 14% was extruded at 160° C. from a nozzle of 66 pores having an orifice diameter of 0.22 mm at a single pore extruding amount of 0.122. The fibrous dope extruded from the nozzle passed an air gap, was drawn therein, passed through a coagulation bath adjusted at about 22° C., continuously washed with five pairs of rollers at a running speed of 200 m/min and dried continuously according to the following drying step without being wound. In the drying, four drying rollers were used and temperature for each of them was set at 180° C., 220° C., 220° C. and 220° C. successively. Retention time in each roller was adjusted at about 17 seconds whereby a polybenzazole fiber where the final water content was 1.1% was prepared. In the resulting fiber, fineness was 110 dtex, tensile strength was 37.5 cN/dtex, elongation at break was 3.1% and tensile modulus was 1170 cN/dtex.

The resulting polybenzazole fiber was used as a core yarn, a substantially untwisted m-aramid dope-dyed staple fiber bundle was arranged around the above in a substantially untwisted state and then m-aramid dope-dyed spun yarn of 60 s cotton count was wrapped in an S twist to give a core-sheath compounded yarn where total cotton count was 15s. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 250 g/m².

Example 2

A polybenzazole fiber which was prepared by the same means as in Example 1 was used as a core yarn, a substantially untwisted polyamide imide dope-dyed staple fiber bundle was arranged around the above in a substantially untwisted state and then polyamide imide dope-dyed spun yarn of 50 s cotton count was wrapped in an S twist to give a core-sheath compounded yarn where total cotton count was 10 s. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 240 g/m².

Example 3

A polybenzazole fiber which was prepared by the same means as in Example 1 was used as a core yarn, a substantially untwisted polyester staple fiber bundle was arranged around the above in a substantially untwisted state and then polyester spun yarn of 50 s cotton count was wrapped in an S twist to give a core-sheath compounded yarn where total cotton count was 10 s. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 260 g/m². Further, the resulting fabric was dyed in black color using a conventional disperse dye followed by drying and setting.

Example 4

The same means as in Example 1 was conducted to prepare a polybenzazole fiber where fineness was 1670 dtex, tensile strength was 37.0 cN/dtex and elongation at break was 3.3% and tensile modulus was 1120 cN/dtex and then 12 fibers were lined up by drawing and subjected to stretch breaking and fine spinning to give a stretch broken spun yarn where fineness was 83 dtex, tensile strength was 19.8 cN/dtex and elongation at break was 4.3%. The resulting polybenzazole fiber stretch broken spun yarn was used as a core yarn, a substantially untwisted polyamide imide dope-dyed staple fiber bundle was arranged around the above in a substantially untwisted state and then polyamide imide dope-dyed spun yarn of 50 s cotton count was wrapped in an S twist to give a core-sheath compounded yarn where total cotton count was 15 s. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 225 g/m².

Example 5

A stretch broken spun yarn where fineness was 74 dtex, tensile strength was 14.6 cN/dtex and elongation at break was 5.5% was prepared, by using the same means as in Example 4, from p-aramid fiber where fineness was 1670 dtex and tensile strength was 20.1 cN/dtex. The resulting p-aramid fiber stretch broken spun yarn was used as a core yarn, a substantially untwisted m-aramid dope-dyed staple fiber bundle was arranged around the above in a substantially untwisted state and then m-aramid dope-dyed spun yarn of 50 s cotton count was wrapped in an S twist to give a core-sheath compounded yarn where total cotton count was 15 s. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 235 g/m².

Comparative Example 1

A polybenzazole fiber prepared by the same means as in Example 1 was used as a core yarn, and a core-sheath compounded yarn of a cotton count of 15s where a polyester staple fiber was arranged at the sheath side was prepared by the means mentioned in the Japanese Patent Application Laid-Open (JP-A) No. 5924/82. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 260 g/m².

Comparative Example 2

A polybenzazole fiber prepared by the same means as in Example 1 was used as a core yarn, and a core-sheath compounded yarn of a cotton count of 10 s where polyamide imide dope-dyed staple fiber was arranged at the sheath side was prepared by the means mentioned in the Japanese Patent Application Laid-Open (JP-A) No. 2003-27380. This compounded yarn was used as warp and woof of a woven fabric to prepare a twill woven fabric where a basis weight was 265 g/m².

A covering property of the fabrics of Examples 1 to 5 and Comparative Examples 1 to 2 was evaluated by naked eye. The evaluation was conducted in five stages ranging from very good to poor where 5 was for very good while 1 was for poor. The result is summarized in Table 1.

Pilling of the fabrics of Examples 1 to 5 and Comparative Examples 1 to 2 was evaluated by a method A according to JIS L 1076. The result is summarized in Table 1.

The fabrics of Examples 1 to 5 and Comparative Examples 1 to 2 were subjected to a continuous irradiation for 100 hours at the irradiating temperature of 63° C. using a xenon weather meter (Ci35AW) and the tear strength after the irradiation was evaluated by a single-tongue method according to JIS L 1096 under the condition where tensile speed was 10 cm/min and test piece width was 10 cm. The result is summarized in Table 1.

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 Covering 4 5 4 4 4 2 2 Property Pilling (grade) 4 4 5 4 4 2 2 Warp Fill Warp Fill Warp Fill Warp Fill Warp Fill Warp Fill Warp Fill Tear Before 283 219 334 263 282 245 255 194 172 169 296 212 198 171 Strength Irradiation (N) After 64 58 69 66 75 81 56 42 69 65 34 28 29 25 Irradiation

The result is as shown in Table 1 and the fabrics using the core-sheath compounded yarn of Examples 1 to 5 exhibited good covering property and pilling and had an excellent resistance to abrasion. Further, those fabrics kept a sufficient tenacity in terms of tear strength after irradiation by a xenon weather meter. On the contrary, the fabrics prepared in Comparative Examples 1 to 2 were inferior to those of the Examples in terms of covering property and pilling.

INDUSTRIAL APPLICABILITY

The present invention relates to an intensified fabric having excellent tear resistance, abrasion resistance, cut resistance and heat resistance and, more particularly, it provides intensified fabric comprising polybenzazole fiber having sensuousness and light resistance by compounding it with other dyeable fiber making the best use of characteristics of polybenzazole fiber having high tenacity and heat resistance. This intensified fabric is useful in, for example, uniform, fireproof clothes, work clothes, outdoor clothing, racing wear or sport clothing used under severe conditions as well as suits, jeans, bag material, roof fabric, gloves, socks, sawing thread, etc. 

1. A core-sheath compounded yarn constituted from a high tenacity and high heat-resistant fiber and other dyeable fiber and/or dope-dyed yarn where the high tenacity and high heat-resistant fiber is arranged as a core yarn while other dyeable fiber and/or dope-dyed yarn are/is arranged in a substantially untwisted state and the surroundings thereof are spirally covered by dyeable fiber and/or dope-dyed yarn.
 2. The core-sheath compounded yarn according to claim 1 where said high tenacity and high heat-resistant fiber is polybenzazole fiber and/or p-aramid fiber.
 3. The core-sheath compounded yarn according to claim 1 where said dyeable fiber and/or dope-dyed yarn are/is m-aramid fiber and/or polyamide imide fiber.
 4. A woven/knitted fabric where the core-sheath compounded yarn according to claim 1 is at least partially used. 